U.S. Pat. No. 6,350,869 discloses the purification of impure cefdinir through the preparation of N,N-dicyclohexylamine salt of 7-[2-aminothiazol-4-yl-2-(z)-hydroxyimino acetamido]-3-vinyl-3-cephem-4-carboxylic acid and subsequent hydrolysis to get pure cefdinir. This process requires the preparation of crude cefdinir, conversion to N,N-dicyclohexylamine salt and then hydrolysis of the salt to get pure cefdinir, and therefore the overall yield is not attractive.
U.S. Pat. No. 5,705,496 discloses a process for preparing the benzathine salt of Cefonicid which comprises treating an aqueous solution or suspension of Cefonicid with an organic solvent and N,N′-dibenzylethylenediamine.
U.S. Pat. No. 5,026,843 discloses the process for the preparation of Ceftriaxone disodium hemiheptahydrate involving condensing 7-ACT with MAEM. The product formed is precipitated by using dibenzylethylenediamine and subsequently is treated with sodium ethylhexanoate in acetone.
In order to get rid of impurities and isolating the product from aqueous medium, all these prior art references used different kind of amine salt with cephem-4-carboxylic acid derivatives. But none of the processes gave desired yield and quantity.
In continuation of our research, for developing new and efficient processes for making cephlosporins, we have found new salts of formula (II) and its use in the preparation of cephalosporin antibiotics of the formula (I) with minimum impurities in high yield.